Method and means for economically drying by air circulation



March 27, 1928. 1,663,982

0. P, M. (3055 ET AL METHOD AND MEANS FOR ECONOMICALLY DRYING BY AIR CIRCULATION Fi led Sept. 16. 1926 2 Sheets-Sheet 1 Ol/der PM. 6035 7T4/p/z 7410300 March 27, 1928. 1,663,982

O. P. M. GOSS ET AL METHOD AND MEANS FOR ECONOMICALLY DRYING BY AIR CIRCULATION Moisture x Z J 7: "3 3 Inuen/ont:

Patented Mar. 27, 1928.

UNITED STATES 1,663,982 PATENT OFFICE.

OLIVER P. M. GOSS, OF SEATTLE, WASHINGTON, AND RALPH H. RAWSON, OF PORTLAND,

OREGON.

METHOD AND MEANS FOR ECONOMICALLY DRYING BY AIR CIRCULATION.

Application filed September'lG, 1926. Serial No. 135,834.

Our invention relates to dry kilns, and particularly to those used for the dryin of lumber, and in which the drying is e ected by the circulation of a body of heated air 6 through the lumber pile.

Heretofore, insuflicient attention has been given to the economical use of this method of drying lumber. When heated air has been repeatedly circulated through the lumber 1 pile it becomes saturated with the moisture absorbed from the lumber to such an extent that the air is no longer fit for further use and must be expelled. In some methods at present the removal of the saturated air is affected by permitting air to escape through roof vents; but this tends to permit too much air to escape at once. In other methods portions of the air in the kiln were permitted to escape through crevices about the door or the stacks of the kiln, which is also unsatisfactory.

In any of said methods the circulated air was removed from the kiln before it had lost its capacity to absorb more moisture from the lumber; and in consequence such proce-.

dure was inefficient, in that it rendered the operation of the kiln too expensive, wasting both heat and steam.

The object of our invention is to dry lumher by a simple, economical, and at the same time efiicient, method of circulating heated air thru the lumber pile.

We attain our object by recirculating the samebody of air continuously through the lumber pile until the circulated air has become so laden with moisture that it settles, by gravity, to the floor of the kiln, from whence it is removed by suction by suitable devices, which devices are also suitably controlled.

Thus the descending column or air has only to travel a short distance to be returned to the ascending column of air, thereby effecting economy of power; besides the body of air is easily moved into circulation; and there is no wasteful consumption of fuel in producing heat and steam. For assuming the ascending column of air, forced up the flue provided between adjacent halves of the pile of lumber, to be raised by suitable steamarrows indicate the circulation of the colheating-coils, located under the lumber pile; to 200 degrees Fahrenheit and the drop in temperature of the descending column to be about 15 to 20 degrees from'the temperature of the ascending column; and assuming the distance between the said columns to be about three and one-half to four feet, it is obvious that it would require but little heat to restore the temperature of the recirculated air to that of the ascending column.

Our theory of the efficiency of our method is as follows:

The continuous circulation of the body of heated air through the lumber pile will cause a portion ofthe, air finally to have absorbed from the lumber such amount of moisture as to render this body of air too heavy for further circulation.

- That is to say, this saturated body of air will be too heavy to be drawn in by the part-lal vacuum created by the heating coils and spray line located under the lumber pile, which of course is the effect produced upon drier portions of air; and consequently said saturated and heavier portions of air Wlll drop by gravity to the floor of the kiln and from there will then be removed by suction as mentioned.

The vents in the floor of the kiln are preferably controlled by gates, which are regulated in turn by an automatic.contrivance, as hereinafter described.

The spray line operates continuously and may be manually controlled. The discharge orifices in the spray line are so small as to maintain the pressure'in the line substantially uniform at all points--that isthere will be a uniform pressure at all points along the spray line regardless of the distance from the source.

We will now more fully describe our invention and its mode of operation with reference to the use of devices shown in the ac- 'companying drawings and specification, in

which: Fig. 1 shows a diagrammatic transverse section of a lumber kiln, and illustrates the operation of our method for drying a pile of lumber by a body of heated air continuously circulated therethru and of which the moistum-saturated, heavier portions are, from time to time, removed by gravity causing these portions to sink to the floor of the kiln, thence to be drawn out by suction throlwh a vent provided in the floor of the kiln; the

umns ofair; the lighter portions of the air, which are drawn back into the ascending column of the circulated body of air are indicated by arrows pointing upward, while the saturated heavier portions of the air are indicated by the arrows pointing downward and leading to said vent.

Fig. 2 is a transverse section of a kiln chamber provided with a number of tracks arranged side by side so as to contain a number of piles of lumber arranged on suitable supports; and this view illustrates that each pile is provided with heating coils, steam sprays and floor vents and further illustrates by arrows the circulation of air as before mentioned, about each pile of lumber in the chamber;

Fig. .3 is a diagrammatic, fragmentary plan of the bottom or floor of the kiln, and shows the heating element, the spray line, the automatic controls for said heating element, the vent in the floor of the kiln, and the automatically controlled gate for such vent; and

Fig. 4 is a fragmentary transverse section of a kiln chamber showing a lumber pile,

arranged over the heating coils and the steam spray and illustrating the thermostatic control of the heating coils and arrangement of the floor vents.

Referring now to Fig. 1, the lumber a is piled in the kiln chamber 1) on suitable sup ports a, over the lie eating coils d, and the,

steam sprays e; The arrows rising from the steam coils and steam sprays indicate the paths followed by the heated air in the kiln chamber which finally descends to the bottom of the kiln and is drawn off through the vents fr and f of the duct f.

The Wet-bulb thermometer g actuates the device it in Fig. 3 to open and close the gate a in the vent f, which leads from the main air shaft j. A motor is operates a fan Z providing the means for drawing the vapor off through the duct f.

A dry bulb thermometer m is provided if desirable to actuate by suitable means a diaphragm valve 'n which will turn oil the heat coils (i should the dry bulb temperature rise above a desired point, and to turn on the said coils when it falls below the desired point.

Suitable vents are provided, but not shown for renewal of the air in the kiln chamber as it is drawn oil through the vent f.

The operation of our invention as set fort in the specification is as follows:

The steam spray e is allowed to function continuously as are the steam coils d, unless it is considered desirable that the latter be thermostatically controlled by a dry bulb thermometer m,in which case as the temperature rises above a determined point set in the actuating device 0, the heat coils (Z will be shut off or throttled until the temperature falls to a point at which the actuating device o is set to turn the heat on a ain.

In either case, whether t e heat is to be continuous or not when the humidity rises above a certain point, also set in the actuating device 0, the wet bulb thermometer g in combination with the said actuating device opening ;0 and the lateral openings p, in the lumber pile, which arrangement of piling lumber is old in the art, but the heat and vapor are not allowed to rise through the top layer of the lumber, hence no openings are provided in the said top layer.

The heat and vapor as it circulates through the lumber cools and falls and is drawn upward again by the under-current created by the heat coils a? and spray line 6 until the air is so heavily saturated as to fall to the floor of the chamber and be drawn oil by the vent f.

As before mentioned when the humidity exceeds a determined point, the wet bulb thermometer will actuate the gate 2' to open, and the fan which is runningcontinuously will draw oil the fallen vapor through the vent in the floor of the kiln chamber until with a battery of kilns.

As it may be lainly seen, convection currents by themse ves, feebly circulate the air in a kiln chamber, but if the circulation of air'is accelerated by heat properly applied and controlled and means provided for drawing off the saturated air, the atmosphere in every part of the kiln chamber will be kept in constant circulation, and there will be no stagnant places and dead spots and thus the desired effect will have been created with the greatest economy of time and money.

The stock coming from the kiln chamber will be of uniform gradefree from injuries and the time of drying will not have been that of the piece of the lumber to dry, but will have been the time taken for the first piece as all the lumber will have been dried at the same time.

We claim:

1. In the method of-drying lumber, piled as described to form a blind flue therein, the

'air under the bottom of the lumber pile being 7 heated, and a s rayof steam injected directly into said ue to induce the heated air to rise therein and spread laterally therefrom, the improvement consisting in removing by mechanically induced suction a portion of the air settling at the bottom of the kiln, relatively to a predetermined condition of relative humidity within the kiln.

2. In the method of drying lumber,-piled as described to form a blind flue therein, the air under the bottom of the lumber pile being heated, and a spray of steam Injected directly into said flue to induce the heated air to rise therein and spread laterally therefrom, the improvement consisting in removing by suction a portion of the air settling at the bottom of the kiln, relatively to a predetermined condition of relative humidity- Within the kiln.

3. In a lumber kiln, in combination with means for supporting a pile of lumber arranged as described to form a blind flue therein, means for heating the air under the bottom of the lumber pile, and a horizontal steam spray line located above said heating means directly under, I and ad acent the -mouth of, and alined with said flue, to induce the heated air to rise in the flue and spread laterally therefrom, a vent located at the bottom of the kiln, means for inducing suction through said vent whereby to remove portions of the air which settles at the bottom of the kiln, and means for controlling said suction, such means including a tem- 1 perature-actuated element located in the kiln.

4. In a lumber kiln, in combination with means for supporting a ile of lumber arranged as described to orm a blind flue therein, means for heating the air under the bottom of the lumber pile, and a horizontal steam spray line located above said heating means directly under, and adjacent the mouth of, and alined with said flue, to induce the heated air-to rise in the flue and spread laterally therefrom, a vent located at the bottom of the kiln, means for inducing suction through said vent whereby to remove portions 0 the air which settles at the bottom of the kiln, and means foropening and closing the vent, such means includmg a temperature-actuated control element located in the kiln.

5. Ina lumber kiln, in combination with means for supporting a ile of lumber arranged as described to orm a blind flue therein, means for heating the air under the bottom of the lumber pile, and a horizontal steam spray line located above said heating means directly under, and adjacent the mouth of and alined with said flue, to induce the heated air to rise in the flue and spread laterally therefrom, a vent located at the bottom of the kiln, power-actuated means for inducing suction through said vent, whereby to remove portions of the air which settles at the bottom of the kiln, and means for controlling said suction, such means including a temperature-actuated element located in the kiln.

6. In a lumber kiln, in combination with means for supporting a pile of lumber arranged as described to torm a blind flue therein, means for heating the air under the bottom of the lumber pile, and a horizontal steam spray line located above said heating means directly under, and adjacent the mouth of and alined with said flue, to induce the heated air to rise in the flue and spread laterally therefrom, a vent located at the bottom of the kiln, power-actuated means' ior inducing suction throu 11 said vent whereby to remove portions 0 the air which settles at the bottom of the kiln, and means for opening and closing the vent, such means including atemperature-actuated control element located in the kiln.

RALPH H. RAWSON. OLIVER P. M. GOSS. 

